Re: ensobj

["Larry Loen" <lwloen@xxxxxxxxxx>]

>In other words, ENSOBJ is only needed to protect  against a non ups
protected power loss??

I believe it could also be used -- albeit at a very coarse, object-level of
granularity -- to guarantee sequences of changes.

I'll express it as if it were in CL for simplicity:

CHGDTAARA CAUTION VALUE('1')
/* do some important stuff that might have to be backed out */
CHGDATARA CAUTION VALUE('0')

should probably be done as follows:

CHGDTAARA CAUTION VALUE('1')
ENSOBJ CAUTION TYPE(*DTAARA)
/* do some important stuff that might have to be backed out, but know that
the data area is '1' if you got here, even if there's a crash */
CHGDATARA CAUTION VALUE('0')
/* from here forward, you know you'v gotten out of the "might have to back
out" section */
ENSOBJ CAUTION TYPE(*DTAARA)

Single level store persistence is not for the faint of heart.  You might
also look into set access state for similar purposes.

Remember that storage management reserves the right to push any change you
make to a permanent object back out to the disk whenever it likes in
whatever sequence it likes.  Modifying persistant storage (if you want to
have any sort of checkpoint/rollback/recovery) therefore takes a bit of
work along the above lines.


Larry W. Loen  -   Senior Java and iSeries Performance Analyst
                          Dept HP4, Rochester MN


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